taylor



June 12, 1923.

C. H. TAYLOR THREAD CUTTER Original Filed March 9, 1916 2 Sheets-Sheet 1 n'uemtoz Win June 12, 1923.

C. H. TAYLOR THREAD CUTTER Filed March Sheet Original 2 Sheets- Eig. 11

Suva-44 5M ma l fob.

. Rem-sailing 12,;1923-. UNITED STATES Re. 15,625 PATENT OFFICE.

CHARLES H. TAYLOB,,OF TORONTO, ONTARIO, CANADA, ASSIGNOB TO'P RATT & WHITNEY comm, OF NEW YORK, N. Y., CORPORATION OF NEW JERSEY.

THREAD CUTTER.

Original Io. 1,878,445, dated August 20, 1918, Serial No. 83,104, filed larch 8,1916. Application for reiuue filed February 12, 1920. Serial no. saunas.

To all whom-it may concern:

Be it known that I, Cumu us HAVEIDCK TAYLOR, of the city of Toronto, Province of Ontario, Dominion of Canada, have invent- 6 ed certain new, and useful Improvements in Thread Cutters, and the'following is a full, clear, and exact description of the same.-

My invention relates particularly to auto- 7 mat-ic machines and has for its object to provide an attachment for machines of this type.

whereby. a thread may bev cut either even with the perimeter of the work, or behind a shoulder, a feature of the invention being that thethread may be but before the piece is separated'from the stock and the thread commencesimmediately at the face of theshoulder- Another feature of the invention is that a thread. may be cut on a reduced diameter between the ends of the bar. either 29 to receive a split nut, or be subsequentlliy divided and form'the screw threaded en s" of separate pieces.

More fully stated the primary ob ect of my ,invention is to provide an mproved milling thread cutter which will operate to cut a thread on" a blank without longitudinal movement of the cutter relative to the blank and which will prevent the formations of facets on thefthread being cut and leave a perfectly smooth and accurately formed I I thread. p

' Further, it is an object of the invention to provide means to rotate the cutter while in operative position and to stop its rotation when in inoperative position.

, Broadly stated, my invention consists of ""aunitary rotary tool of circular form with its perimeter divided into a plurality of threads, each thread being divided into a plurality of cutting teeth. -The number of these cutting threadsin'the embodiment illustrated is .not an'aliquotyor commensurate part of the number of cutting teeth in'each thread. The threads are spaced uniformly around the surface'of the tool and are similar in cross section to the threads desired to be cut. The tool is. as before mentioned,rotary,

and it is combined with a chuck, or otherstock holding. means also having rotation o imparted to it,'an'd the relative speed of the cutter and the stock or bar is an imre portantfactor. The stock must be driven at as many tin-res greater speed than the tool as there are threads on the tool, the effect being that one continuous thread is cut on the stock equal inlen h to the width-of the tool and possessing a. ead equal to a fraction the thread of the tool is of its lead. v I have illustrated and will describe my invention appliedto an automatic machine having a collet for holdi .the stock and feedin mechanism .by which the stock is intermittently fed through the collet, and a. pair of, alternating cross slides carryin respectively my improved. cutting tool and a cutter for separating the finished piece from the stock. For' full comprehension, however, of my invention, reference 'must be had to the accompanylngdrawingsin which similar reference characters'indicatethe same parts, and wherein:

Figural is a transverse sectional view of a, machine of the type mentioned and equipped with my invention.

Figs. 2 and?) are side elevations of my im-.

proved cutter removed.

milling cutter removed and drawn to a larger scale, the cutter being illustrated in process of. manufacture with the threads formed on the perimeter. and partially toothed. i

Fig. 6 isa sectional view. of the annular member upon which thecutter is mounted. 'Fig. 7 is an elevation of aportion of a lathe for carrying myimproved-attach'ment and .il lustrating the attachment in vertical section. Fig. Sis a plan view of the attachment. Fig. 9fis a diagonal sectional view taken on line 9-9 of Fig. 7.

F1 g. 10 is a diagram of the gears for 0htammg the required relative milling speeds of the cutter and stock.

Fig. 11 is a detail end elevation of the head and driving mechanism for the attachmerits.

F g. 12'is a plan view of the attachment shown in place in a lathe.

The frame of the automatic machine to which my invention is applied is indicated at 2, having cross slides'at 3 and 4. the collet at 5. the cams for operating the slides at 6 and 7. and the levers effecting the operative connection between the cams and slides at 9, l0 and 11 My improved thread cutter has a milling action and is incor rated in an attachment mounted upon slide 3, and the cutter by which the finished piece is separated from the stock is carried by an attachment 16 mounted rigidly on the slide 4.

In the present application of my invention, my screw thread milling cutter consists ofian annular member 20, although for other requirements the particular form may be changed, the milling face or perimeter of the cutter being the essential feature.

This millin face or perimeter is cut to present six ind ependent and separate threads 21, 22, 23, 24, 25 and 26 respectively, each thread being cut to present a plurality of teeth as illustrated in Fig. 4. These-threads commence atone end or side of the cutter at intervals of i; the circumference and extend parallel around the cutter, finishing at the other end or side. They have corresponding leads and each lead is approximately the axiallength of the. milling face.

The number of independent threads on the cutter maybe varied. It is, however, essential to the present inyentioii that the threads have multiple 'starts,; that is, that a plurality of separate helices, be provided on the thread cutting surface. The multiple starts or individual helices are uniformly spaced about the periphery of the cutter and preferably have a form and size conforming to the thread desired to be cut.

The lead of these cutter threads or helices is increased to a multiple of the lead or the thread. desired to be cut, and so increased that it .will preferably correspond toPthe number of starts or helices provided on the cutter. In other words, if' the number of starts chosen for the cutter is 6, as in the present illustrated form of the invention, the lead of the threads on the cutter would be increased six times as compared with the lead desired to be cut. If, however. the number of helices on the cutter is four,.the lead would preferably be increased but four times c ompared to the lead of the thread to be cut;

In order to present an oblique arrangement of teeth across the face of the cutter, I cut the periphery of the cutter by means of oblique or helical gashes as shown in Fig. 4. thus providing the preferred form of cutting edge on the cutter, the number of gushes corresponding to the number of cutting edges.

In order to" obtain all of the benefits of the present invention, the number ofthreads or starts on the cutter should be a-liquant or incommensurate with the number of teeth on the cutter. I have shown. in the embodiment of the invention.illustrated and de scribed, the cutter 20 provided with 71 teeth. but any other number of teeth may be pro vided so long as the multiple of the threads on the cutter is an aliquant part of the number of teeth. The function ofthis incommensurate ratio between the number of threads and number of teeth is primarily to prevent the formation of facets or irregularities in the thread being cut.

so lon as this incommensurate ratio is maintained the teeth in each of the independent threads of the cutter will engage slightly different points in the circumference of the blank being threaded. The rotation of the blank and cutter are commensurate with relation to each other while the numbe of teeth engaged by one rotation of the cut ter is incommensurate. The entire periph-' ery of the blank is engaged while the cutter rotates through a portion of a revolution, the portion of the cutterengaged being dependent upon the multiple starts and multiplied lead of cut-ter threads. As the successive teeth on the different helices are spaced an incommensurate part of a circumference, the successive portions of the cutter will have their teeth so spaced that the blank will be engaged at slightlydifl'ering points in its circumference. In the embodiment of the invention shown the teeth of each portion of the cutter will be incommensurately related to those of the preceding portion so that the engagement of the different teeth of the cutter on the blank will be progressively different in each portion of the cutter.

In order to obtain the correct relative speeds of the stock and the milling cuttelz. I have designed a special attachment including the necessary gears and carrying the aunular member 20 which has the milling face above described cut upon its perimeter and I will now describe this attachment. It consists of a pair offrames 30 and 31 which are left and right halves of the attachment respectively. Theleft half ofthe frame has a nb 32 which engages a corresponding function is accomplished for the reason that groove'in the cross slide to which it is fastened by bolts or'by screws. The right half 31, is boltedto and carried by the lefthalf and between them is mounted an internal gear 35. one end of which" is of reduced diameter 36 and cut on its outside 'with a left hand thread. This end of the internal gear has screwed thereon -the an-' nular milling cut-ter. the cutting face of. which protrudes from the forward face ,3? of the. attachment. 'ILhis internal gear is driven from a chuck or main driving gear 40 of the machine, which gear is driven in the direction indicated and drives a. pinion 41 on the shaft of which a second pinion 42 i is also rigidly mounted. This latter pinion 4-2 is the driven element "with which the driving gear of the attachment comes into operativeengagement when the cross slide. 3 is moved to an operating position.

The gears of the attachment consist of I theinternal gear 35 and a train of gears 43, 44 and 45, the latter being mounted rigidly upon a shaft upon which is also rigidly mounted a gear 47 adapted to come into mesh with gear 42 when the slide 3 is shifted to operating position. This system of gearing is adapted to impart to the milling cutter a speed of one revolution to six revolutions of the stock.

In other words, while the stock rotates. once, the milling cutter rotates {of a revolution. This ratio is necessary in the embodiment of the. invention described for the reason that the lead ofthe threads is increased six times relative to the work and the number of starts of the threads on the cutter is also six. -This ratio must, how

ever, be changed dependent upon the multiple of the starts'on the cutter and their lead; As it is an important factor that these relative speeds be obtained,- I will describe the gears specifically in tabulated form:

Gear. Teeth. Pitch.

ation may be any of the well known-types.

of stock feeding devices, Ihave neither described nor'illustrated the latter, but it will be understood nevertheless that the stock is advanced as required after each threading and severing operation. The finished piece is severed from the stock by a cutting tool mountedin the carrier 51 fastened rigidly to the slide 4.

Other tools may be mounted on the an? tomaticv or other machine upon which the present invention may be provided as an attachment. These tools may be preferably held as usual in .a turret 52 or other mounting whereby the piece being screw threaded by my milling cutter may be also operated upon in any of the usual ways, the milling operation taking place at any convenient time during the fashioning of thepiece.

' Itwill be obvious from the above that my thread milling attachment requires no longitudinal movement, that'is, no movement parallel to the axis of the blank being threaded; also it will be understood that the present milling operation may take place at any point in the length of the blank being operated on, either-at its outer free end or at the end adjacent the point of severing from the stock, and that the intermediate portions of the blank may be of larger or smaller diameters, the method of milling by the present invention permittin a screw thread to be milled at any part of t e blank.

Operation,

During the milling operation the toothed cutter and stock rotate inthe same direction and their contacting faces rotate in opposite directions, and as the stock makes six revolutions to one of the toothed cutter, a'cont-inuous screw thread is cut in the perimeter of the stock having a lead one sixth the lead of the cutter and equal in length to he axial length of theface of the cutter.

In orderjto produce a double, triple or quadruple thread, the driving gears should be changedto rotate the cutter g, i or Z; the number of revolutions of the stock.

flThe, greater number of teeth on the cutter with proportionately less number of revolutions of the cutter, the more perfect the edge of the threads milled, and the fewer the number, the rougher the edge, while the number of threads govern the speed of both the cutter and stock'which may be varied to ive the proper. cutting speed.

n cutting threads by the above described method, it is essential that the circumference of the blank being threaded should be touched by as many teeth vin the cutter as possible and at slightly different positions in the circumference, otherwise irregularities such as facets will be formed. It is'possible, and well known, to mill screw threads with a cutter having a single thread conforming to the shape and size. desired to be cut and rotated at the same annular velocity as the blank. This, however, has the. disstart thread is used. When this is done the I angular speed is reduced in proportion to the number of starts or independent threads on the cutter. of the cutter is formed into a number of cutting. teeth which is a multipleof the number of starts, it will be evident that the different arcs in the periphery of the cutter will engage precisely the same points .in thecircumference of the blank, which points on the blank would be slightly separated from each other and would thus form facets. To avoid this form-ation of facets and irregularities, I cut the threaded periphery-of the cutter into a number of teeth incommensurate with the number of starts or the lead of the cutter advantage of requiring a high rotative speed If, however, the periphery I threads, .that is, the multiple of the lead of r the blank, the teeth in the different portions of the cutter will engage points in the blank at slightly different points. Looked. at in. another way, by dividing the circumference helix are spaced. a number of teeth plus a fraction from the teeth of the successive helices, thus as each individual helix. op-

erates upon the blank from one face to the other of the cutter, successive helices cut at slightly'differing points in the blank.

} mm the foregoing it will be seen that my improved milling cutter performs its function without axial movement of either the cutter or the stock, and the multiple quality of the cutter may be increased or dimin ished without departing from the spirit of my invention.

What I claim'is:

1. In a milling screw-cutting attachment for an automatic screw machine a frame adapted to be incorporated in the machine,,

an internal gear mounted in the frame, an annular cutting member mounted upon said gear, and means for driving the gear.

2. A milling screw-cutter having aneven number of toothed helical threads and each thread having an odd number of teeth.

3. A milling screw-cutter having an even number of toothed helical threads uniformly spaced around the periphery of the cutter and each thread having an odd number of teeth.

4. A milling screw-cutter having toothed helical multiple threads uniformly spaced around the periphery of the cutter, the

threads having corresponding number of teeth and the number of threads being an aliquant part of the number of teeth of each thread.

5. The combination with a screw-cutting machine frame and a rotary stock-holding collet,' of a milling screw-cutter having toothed helical multiple threads uniformly spaced around the periphery of the cutter.

.the threads having corresponding number of teeth and the number of threads being an aliquan't part of the number of teeth of each thread, and means rotatively connecting the collect. and cutter whereby the latter is ro tated a fraction of the revolutions of the collet equal to number of threads into which the lead of the cutter is'divided.

-6., A milling screw-cutting attachment for an automatic screw machine' comprising a frame adapted to be incorporated in the machine, a gear rotatably mounted in the frame: an annular member rigidly mounted upon the gear and having toothed multiple threads and the number of threads being an al iriuant part. of the number of teeth f each thread a driving gear rotatably mounted in the frame; and a train of gears rotatively lei-nal connecting the driving gear to the internal gear.

- 7. A milling screw-cutting attachment for berrigidly mounted uponthe gear; a driving gear rotatably mounted in the frame; and a train of gears rotatively connecting the driving gear to the first mentioned gear.

8. Ina screw-cutting machine a mi ling screw-cutter, means for rotatin'gsaid cutter, and a contmuously rotating mechanism for I driving said means, such means being normally 1n operative engagement Wit-l1 said mechanism and adapted to be moved out of engagement fiierewith.

9. 111.1. screw-cutting machine, the combination with a rotary stock carrier and a slide, of a milling screw-cutting attachment comprising a frame mounted upon the slide; an annular member rotatably mounted upon said frame, the perimeter of saidmember having uniformly circumferentially ,spaeed toothed multiple peripheral threads, means for -rotating said annular member, said means including an intern-a1 gear, and gears adapted to impart rotation to the internal gear whcn'the slide is shifted.

10. In a screw-cutting machine, the combination with a rotary stock carrier. a tooldriving gear in rotative relation therewith, :ind a, pair of cross-slides with means for reciprocating the same, of a milling screwcutting attachment comprising a frame,.

ber with a portion of its outer perimeter' protruding heyond the frame, and the said perimeter having uniformly circumferentially spaced toothed multiple peripheral threads: a driven gear rotatably mounted within the frame and arranged to engage the said tool-driving gear when the slide is shifted in one direction; and a train of gears rotatively connecting the driven gear to the internal gear.

11. In a screw-cutting machine.- the combination with a rotary stock-carrier. a tool driving gear in rotative relation therewith, and a pair of cross-slides with means for reciprocating the same, of a milling screwcutting attachment comprising a frame, means fastening the frame to one of the crossslides; a cylindrical member rotatably hearing within the frame and having ingear teeth: an annular member mounted rigidly upon one'end of the. cylin- 1 ing cut.

cumferentially spaced toothed multiple mounted -within the frame and arranged slide is shifted in one direction; a train of mounted on the other slide and arranged to sever.

on one of its surfaces multip start threads conforming to the shape of threaddesired to be cut, each of said threads being interrupted to form a number of cutting-edges the cuttin edges so formedin each threa engaging ifl'erent points in the threads be- 13. A screw thread millin cutter having on one of its surfaces multip e start threads conforming to the shape of thread-desired to be cut, each of said threads being interrupted to form, a number ofcutting edges,

enga in ro ssively different points in the tl mre d be g cut. 7

14. A screw thread milling cutter havin multiple start threads uniformly space around its periphery, each thread bein divided into a, number of cuttin teeth w ereby the teeth on the different circumferential portions of the cutter will contact with different points in the periphery of the threads being cut. v I

15. A screw thread milling'cutter having uniformly spaced on one of its surfaces multiple startthreads conforming to the shape of thread desired to'be cut, each of said threads being interrupted to form a number of cutting edges, the cutting edges so formed in each thread engaging dlfl'erent points in the threads being cut. 16. A screw thread milling cutter having on'one of its surfaces threads conforming .to the shape of thread to be cut, saidthr'eads having a lead {which is a multiple of. that desired to be cut, said cutter adapted to be rotated relative to the blank to be threaded at a speed the 'reciprocal of the multiple lead of the cutter threads, said cutter having its threaded surface divided into cutting edges by generally axial grooves, the number of cutting edges. formed thereby being incommensurate with the multiple lead of the cutter threads.

17. A screw thread milling cutter having on one of its surfaces .a thread conforming to the shape of thread tobe cut, said, thread having a lead which is a multipleof that desired to be cut, s'aid cutter adapted tO'b rotated in an axis parallel to the axis of the blank relative to the blank to be threaded at a speed the reciprocal of the multiple lead of the cutter thread, said cutter having its threaded surface divided into cutting edges by generally axial grooves, the numberof ripheral threads; a driven gear rotatably to engage the said tool-driving gear when the gears rotatively connecting the driven gear, to the internal gear; and a cutting tool 12. A screw thread millin cutter having the cutting edges so formed in each thread cutting edges formed thereby being incommensurate with the multiple lead of the cutter thread. I

18. A screw thread milling cutter having on one of its surfaces multiple start threads conforming to the shape of thread to be cut, and adapted to be rotated relative to the "blank to be threaded, said cutter having its of the cutter adapted to be rotated relative to the blank to be threaded, said cutter having its thread.- ed surface divided into cutting edges by generally axial grooves, the numberzof cuttin edges being incommensurate with'the mu tiple of the cutter threads.

e 20. A screw threadrmilling cutter having a on one of its surfaces threads conforming to the shape of thread to be cut, said threads havlng' a lead which is a multiple of that desired to be cut, said cutter adapted to be rotated relativeto the blank to be threaded at a speed the reciprocal of the multiple lead of the cutter threads, said cutter having its threaded surface divided into cutting edges by enerally. axial grooves but at a small ange to the axis, the number of cutting edges formed thereby being incommensurate with the multiple lead of the cutter threads.

21. A screw thread milling cutter having on one of its surfaces a thread conformin to the shape of thread to be cut, said threa havin a lead which is a multiple of that desire to be cut, said cutter adapted to be rotated in an axis parallel to the axis-of the blank relative to the blank, to be threaded at a speed the reciprocal of the multiple lead of the cutter thread, said cutter having its threaded surface divided into cutting edges by enerally axial grooves but at a small ang e to the axis, the'number of cutting edges formed thereby being incommensurate with the multiple lead of thecutterthread.

22. A screw thread millin cutter having on one of its surfaces multip e start threads conforming to the shape of thread to be cut,

and adapted to be rotated relative tothe blank to be threaded, said cutter having its threaded surface divided intocutting edges by'generally axial grooves but at a small angle to'the axis, the number of cutting edges formed thereb being incommensurate with the multiple of the cutter threads.

23. A screw thread millingcutter having on. its periphery multiple start threads conforming to'theshape and size to be cut, and ada ted to be rotated relative to the blank to be t readed, said cutter having its threaded surface divided into cutting edges by generes formed thereby being incomally axial grooves but at a small angle to the axis, the number of cutting edges being incommensurate with the multiple of the cutter threads.

24. A screw thread milling cutter, said cutter being provided with screw threads having a lead which is a multiple of that desired to be cut, said cutter being rotated relative to the blank to be threaded at a speed the reciprocal of the multiple lead of the cutter threads, and said cutter having its threaded surface divided into cutting edges, the number ofcutting edges being incommensurate with the multiple lead of the cutter threads.

25. A screwthread milling cutter having screw threads conforming to the cross section of thread desired to-be cut, the lead of the threads on the cutter and that to be cut' being gashed to form a number of cutting teeth in said cutter incommensurate with the multiple lead of the threads on the cutter.

27. A screw thread milling cutter adapted to be rotatably mounted in an axis parallel with the blank to be threaded, said cutter having threads conforming to the shape to be cut and having a lead which is a multiple of that desired to be cut, said cutter being rotated at a speed relative to the blank which is a reciprocal of the multiple lead of the cutter threads, said cutter having its threaded surface divided into cutting edges by generally axial grooves, the cutting teeth bein differently disposed in different arcs of the cutter.

28. In a screw cutting machine, a screw thread millingcutter, and means for rotating said cutter, said means being in engagement with said cutter when the cutter is in operative position and disengaged therefrom when the cutter is in inoperative position.

29. In a screw cutting machine, a screw thread milling cutter, means for rotating said cutter, means for feeding said cutter into operative position with a blank to be threaded. and means operating simultaneously with said feeding movement to engage said rotating means with said cutter when said cutter is'in operative position.

30. In ascrew cutting machine, a screw thread milling cutter, means for rotating said cutter, and means for feeding said outter into operative position with a blank to be threaded, said rotating means being oper- -'oif said blank after the milling operation is atively connected with said milling cutter during the movement of the cutter into operative position, and disengaged from said cut- -ter during the movement of the cutter out of engagement with, the blank.

31. An automatic machine comprising in combinatiommeans for rotating a blank, a thread milling cutter having a helix on one of its surfaces, means for rotating said outter at a predetermined speed relative to said blank rotation, means for feeding said cutter toward said blank, and means permit-- ting additional operations' on the blank;

32. An automatic machine comprising in combination, means for rotating a blank, a thread milling cutter having a helix on one of its surfaces, means for rotating said cutter at a predetermined speed relative to said blank rotation, means for feeding said cutter toward said blank, and means permitting additional operationsfon the blank, including means for cutting off s'aid' blank.

33. An automatic machine comprising in combination, means'for rotating 9; blank, a thread milling cutter having a'helix on one of its surfaces, means for rotating said outter at a predetermined speed relative to said blank rotation, means for feeding said outter toward said blank, means permitting additional o erations on said blank, means for cutting 0 said blank, and means permitting advancing'a-new blank into operative position.

34. An automaticmachine comprising in combination, means for rotating a, blank, a thread milling cutter having a helix on one of its surfaces, means for rotating said cutblank rotation, means for-feeding said outter toward said blank, and means for cutting completed.

35. An automatic machinecomprising in combination, means for rotating a blank, means for rotating a thread millingcutter having a helix on one of its surfaces at a predetermined speed relative to said blank rotation, means for. feeding said-cutter toward said blank, and means for, cutting off said blank operating in timed relation to 116 said milling cutter.

36. An'aptomatic machine comprising in combination, means for rotating a blank, a thread niilling cutter having a helix on one of its surfaces, means for rotating said cut'-- 120 ter at a predetermined. speed relative to said blank ,rotation, means for automatically feeding said cutter toward said blank, and means for cutting off said blank after the milling operation is completed.

37. An automatic machine comprising in combination, means. for rotating a blank, (a thread milling cutter having a plurality ofgenerally circumferential rows 0 cutting edges, said cutter being mounted on a cross 139 slide of said machine, means for feeding said cutter toward said blank, and means for cutting off said blank mounted on a cross slide oppositely disposed to the slide on which said milling cutter is mounted.

38. An automatic machine comprising in combination, means for rotating a blank, a

a thread milling cutter having a plurality of generally circumferential rows of cuttingedges, means for rotating said cutter, means for feeding said cutter toward said blank, means preventing axial movement" of said H cutter, and means permitting additional operations on the blank, including means for cutting ofl said blank.

40. An automatic machine comprising in combination, means for rotating a blank, a thread milling cutter having a plurality of generally circumferential rows of 'cutting ed es, means for rotating said cutter, means or feeding said cutter toward said blank, means permitting additional opera.-

tions on said blank, including means for cutting off said blank, means preventing axial movement of said cutter, and means permitting advancing a new blank into .operative position. I

41. An automatic machine comprising in combination, means for rotating a blank, a thread milling cutter having a plurality of generally circumferential rows of cutting edges, means for rotating said cutter, means for feeding said cutter toward said blank, and means for cutting off said blank, said last mentioned means operating in timed relation to said milling cutter.

42. An automatic machine comprising in combination, means for rotating a blank,-

a thread milling cutter having a plurality of generally circumferential rows of cutting edges, means for rotating said cutter, means for feeding said cutter toward said blank, means preventing axial movement of said cutter, and means for cutting off said blank after the milling operation is completed.

43. An automatic machine comprising in combination, means for rotating a blank,

a thread milling cutter having a plurality .of generally circumferential rows -'of cutting edges, means for rotating said cutter, means for automatically feeding said cutter toward said blank, and means for cutting off said blank, said last mentioned means operating in timed relation to said milling cutter,

" 44. An attachment for an automatic machine having a cross slide and a spindle comprising in combination, a body member adapted to be attached to the cross slide on said machine, a thread milling cutter mounted on said body member in an axis parallel to the spindle on said machine, and means to rotate said cutter in timed relation to said machine-spindle when said cutter and body member are in operative position. i

45 An attachment for an automatic machine comprising in combination, a body .member adapted to be attached to a cross slide on said machine, a thread milling cutter mounted on said body member in operative position relative to the spindle of said machine, and means to rotate said cutter in timed relation to said machine spindle.

46. An attachment for a scre'wmachine comprising in combination, a body member relation to a spindle on said machine, and

means to rotate said cutter in timed rela' tion tosaid machine spindle.

47.'An attachment for a screw machine comprising in combination, a.body member adapted to be attached to a movable part of said machine, a thread milling cutter mounted on said body member in operative relation to a spindle on said machine, means to prevent. axial movement of saidcutter, and means to rotate said cutter in timed relation to said machine spindle.

48. For use in milling screw-threads, a multiple thread hob having equally spaced transverse chases whereof the total number,

lus or minus one, is divisible by the numr of threads constituting the multiple thread employed.

49. For use in milling screw-threads, a four-threaded hob having equally spaced transverse chases whereof the total number, plus or minus one, is divisible by four.

In testimony whereof, I hereto aflix my 

